Fig. 1. Preparation and characterization of CISP.

a Representative fluorescence images of PD-1-APC on cell membrane (n = 5 technical replicates). Scale bar = 10 μm. b The expression of PD-1 on cell membrane detected by flow cytometry (n = 3 technical replicates). c Schematic illustration showing the process to prepare low-cholesterol membrane. d Relative level of cholesterol in cell membrane after cells incubated with different concentration of (2-hydroxypropyl)-β-cyclodextrin (β-CD) for 0.5 h (n = 3 independent samples). e Representative TEM images of QFN₇₁₇, nCSP, nCISP and CISP (n = 3 independent samples). Scale bar = 50 nm. f The localization of cell membrane (marked with DiD) and QFN₇₁₇ core (marked with coumarin) in CISP, and the fluorescence intensity of DiD and coumarin on the arrow line. B16F10 cells were incubated with CISP for 4 h (n = 3 independent samples). Scale bar = 5 μm. g Western blot analysis of PD-1 and Na⁺/K⁺-ATPase in membrane of CTLL2 (CTLL2-M), membrane of CTLL2-PD1 (PD1-M), nCSP, nCISP and CISP. h Schematic illustration showing nCSP, CSP, nCISP, CISP and CIP used in this study. Data represent mean ± SEM (d). Statistical significance was determined by one-way ANOVA test in d, and it was two-sided and adjustments were made for multiple comparisons. The experiments for a, b, d–f, g were repeated three times independently with similar results. Source data are provided as a Source Data file. MFI mean fluorescence intensity, QFN Quercetin-ferrum nanoparticles, QFN₇₁₇ QFN loaded with SR-717, nCSP normal-Cholesterol cell membrane-coated QFN₇₁₇, CSP low-cholesterol membrane-coated QFN₇₁₇, nCISP normal-Cholesterol cell membrane-coated ICB agent and QFN₇₁₇, CISP low-cholesterol membrane-coated ICB agent and QFN₇₁₇, CIP low-cholesterol membrane-coated ICB agent and QFN.